Flat Roof Lead Flashing Sagging

[newbie99]

I have used lead flashing adhesives to glue down the lead. But. Have noticed there is some damp coming through the flat roof. The work was done over 10 years ago and the lead was not tugged into the chased brickwork as it was not easy to locate the mortar, i.e the wall was rendered.

My question is: is it a good idea to use heat gun to heat that lead flashing and remove it and then refit it. But this time use screws to hold the flashing. Is this feasible? Other suggestions are welcome...

[The Builder]

The first thing I would do is to chase the flashing into the wall properly. There's no need for a mortar joint. You need an angle grinder (9" / 225mm) to cut a chase as deep as possible, probably around 50mm.

A common way to fix the flashing to the wall is to ...
Beat the lead absolutely flat, then slot it into the chase horizontally.
Fold a few pieces of spare lead into "lead wedges". Drive a few of these into the chase immediately above the lead.
Dress the lead down vertically to cover the felt upstand.
Re-point the chase.

If you don't get on with the wedges, then squirt silicone sealant right inside the chase, leaving enough room for re-pointing.
This way, you'll have to leave the silicone overnight to go off before dressing the lead down.

[newbie99]

Thanks The email Builder for your guide. I will look into chasing the mortar when I start work in the bank holiday weekend have coming up.
However, when we had heavy downpour recently I noticed there was about an inch of standing water. The edge of the roof where the water meant to drain off have a height and that also need looking into why it's a that height. Hopefully it just has lifted from the adhesive so could be reseated.
If that edge is badly fitted such that it caused the height, is there any remedy to this?
Also what are the original pebbles meant to do? When the felt was removed and replaced, the pebbles were also removed, and wonder if this meant to stop the standing water as the pebbles make the roof even at the edge of the roof??